osi madison



Patent-ed Sept. 23, 1919.

A. w. sc HonGER.

DRY CELL. APPEICATION FILED Nov.19.191s.

AIRLIE SCHORG-ER, OF MADISON, WISCONSIN, ASSIGNORTO lIBUllEtGrESS BATTERY COMPANY, 0F 'MADISOIYL WISCONSIN, A CORPORATION OF WISCONSIN.

DRY CELL.

Specification of Letters Patent.-

lPatented Sept.. 23, 1919.

To all whom t may concern:

Be it known that I, ARLIE W. SoHoRGER a citizen of the United States, residing at Madison, in the county of Dane and State of Wisconsin, have invented certain new and useful Improvements in Dry Cells; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

Electric dry cells can be roughly grouped into two general classes. In the first class, as illustrated, for instance, in Burgess and Hambuechen U. S. Patent Number 1,032,529, issued July 16, 1912, the .zinc can is lined with paper or other equivalent bibulous material and the so-called mix consisting of carbonaceous material, manganese-dioxidl' and-the usual salts and moisture is tamped about a carbon rod, thereby forming the cathode which is spaced from the zinc or anode by the layer of moistened paper.

In the second class, the mix, before its introduction into the zinc can, 1s molded aboutfthe carbon rod to form a so-callcd core which, though fragile, is nevertheless capable of manipulation on a factory basis. A suitable apparatus for thus molding the moist miX about a carbon rod is disclosed in U. S. Patent to Hambuechen Number 1,232,297, issued July 3, 1917. The core so formed is next wrapped about with gauze, cheesecloth or the like, held in place by rubber bands or by a wrapping of thread, as disclosed in Burgess U. S. Patent Num- -ber 1,162,449, issued- November 310, 1915. The wrapped core is then introduced into the zinc can, and an electrolyte in the form of a gelatinizable paste is poured into the annular space separating the core from the wall of the zinc can. It is quite customary to gelat-i'nize this paste by a cooking operation, and the gauze wrapping prevents disintegration and washing away of the molded mix during the cooking, and, of course, prevents the mix from crumbling away and dropping into contact with the zinc during theA preceding operation of assembly. These cells are ordinarily said to be of the bag type because the gauze Wrapping forms in effect a bibulous bag to hold the mix in position during assembly and during cooking of the gelatinizable electrolyte.` After thel electrolyte has been hardened to a jelly-l like consistency,` the gauze wrapping is no longer essential, and in fact its presence in the cell presents some objections, as will be well understood fby those skilled in the art.

,',lhe Apresent invention relates to galvanic cells of the bag type and has as one of its objects the elimination of the gauze bag and the substitution vfor it during assembly of a hard, thin and porous covering put on by dlpping the molded core into a magma such as a mixture of plaster of Paris and water.

It is a further object of the present invention to simplify and cheapen the process of manufacture by eliminating the expensive gauze' bag and the tedious and expenslve operations of wrapping the core with the gauze and binding lit in place with. a wrapping of thread or the like. 4

It is a further object to produce a finished battery of the bag type of high output, low internal resistance and good shelf life, as the results of this new method of production and this new'structural arrangement of the core or cathode of the cell.

The accompanying drawing, (Figure 1) illustrates, somewhat diagrammatically, a cell constructed in accordance with the present invention. Fig. 2v shows a modification. In the drawing, 1 is the zinc can serving as anode and also as a fluid tight container for the other elements of the cell; 2 is the gelatinized electrolyte; 3 is a carbon rod enveloped in the molded mix 4 of carbonaceous material, manganese dioxid, etc., and 5 is the envelop or bag of hardened plast-er dip. The carbon rod may have a brass terminal cap 6, a pitch seal 7, a cardboard washer 8, and an air space 9, as is usual in dry cell construction, and may beI of any desired size, as, for instance, six inches high to conform with standard telephone practice, lor of a much smallersize for use in battery hand lamps and like novelties.

The process of assembling the component arts to make a cell of this construction 1s as follows: The mix 4 is molded about the carbon rod 3 in a suitable tamping machine, as of the construction shown in Hanibuechen Patent 1,232,297, and the fragile core thus formed is dipped into a magma, preferably consisting essentially of a suspension of plaster', such as plaster of Paris, in Water, so that after dipping` the core will be covered with a thin film of the dip which on hardening willv form an envelop for the molded. part of the core. The film of dip can be relatively thin and will harden quickly to form a substantially continuous, uniform membrane or bibulous envelop. As a factory expedient,the dip may be allowed to harden while the cores rest on a greased plate or on a smooth bed of sand. This prevents sticking to the support, and when sand is used, a certain amount clings to the bottom of the core, as illustrated diagrammatically in the drawing at 10, where the core rests on the zinc bottom of the can. These particles of sand then act to separate and insulate the core from the bottom of the Zinc can and obviate the need for covering the zinc bottom with a disk of paraffin paper, as is common practice, or the need for impregnating the lower portion of the core with parafiin, as described in Burgess Patent 1,162,4fl9. There is thus obtained some saving in labor and some economy in material.

After the core has become thoroughly hardened on the greased plate or on the bed 'of sand7 it is introduced into its zinc can and the electrolyte is poured into the annular space between the core and the zinc can. in accordance with the usual practice of assembling` bag type cells. TheI gelatinizable electrolyte may consist of a mixture of cereals and zinc and ammonium chlorids. capable of gelatinization on heating, though I prefer to use a water solution containing about 25.5% of cereals, say, cornstarch and cornmeal, and 36.79? ot' zinc and ammonium chlorids, all at a temperature considerably lower than room temperature for this mixture, though not original with me, is of such a characteras to function in advantageous manner as a part of a cell, more particularly because it gelantinizcs without the need for a subsequent cooking operation.

'The magma into which the cores are dipped to form the film which subsequently hardens to a coherent bibulous envelop may vary in composition, and there are hereinafter described several which are suitable, and some of which offer Special advantages.

Pla-ster only/. A'mixture of water and plaster in suspension forms a suitable dip. Thus I may use 225 grams plaster of Paris and 250 grams of water. A core dipped into such a suspcnsion'takcs on a 'ilm which on drying hardens into a porous, continuous, strong cup or envelop completely surrounding the core. The proportion of plaster of Paris to water may be varied through relatively wide limits in order to vary the thickness of the hardened film, for the thinner the magma theI thinner will be the film produced on the core. Another suitable mixture consists of 20 gramsainc oxid. 20 grams zinc chlorid, and 10 grains' Water.l Also, there may be used 20 grams magnesium oXid; 20 grams magnesium chlorid, and 150 grams water. l

With the foregoing plaster of Paris mixture, the envelop is quick setting on the core and is highly porous and is insoluble in the electrolyte of the cell. In fact, the quick setting character of the dip presents some difficulties from a manufacturing standpoint, in that the mixture sets relatively ouiekly in the dipping vessel, thereby causing some waste of material. I have discovered that these difficulties can be overcome by the addition to the dip of a suitable salt to act as a retarder to the setting of the laster.

Plaster and salt-A suitable ipping magma may consist of 225 grams of plaster of Paris and 225 cubic centimeters of 2% sodium borate solution. The sodium borate acts as a retarder to delay setting of the magma. For example, a plaster alone which would set in five minutes in the dipping vessel can be so retarded by the addition of a small amount of borax that it Will not set for ten to twenty hours. In a thin film on the cores, however,- it will set in one hour, and this is rapid enough for commercial practice. Analogous salts of boric acid can likewise be used, and even other salts, so long as they would not be harmful 1n the battery. -I have found that sodium borate is entirely harmless.

Plaster and colloidal suspensions-As a substitute ,for sodium borate or other salt to retard the setting of the plaster dip, I may use colloidal suspensions such as starch, agar agar and the like. In addition to prolonging the time of setting, these colloidal suspensions give certain desirable characteristics to the finished cell. For instance, starch when acted on by zinc chlorid has the property of swelling or expanding. If it is incorporated into. the core coating with the plaster, it remains 'intact While the core is out of contact with the electrolyte. When the electrolyte is poured around the core, the zinc chlorid of the electrolyte gradually attacks the starch and expands the particles. This breaks up or shatters the core coating and allows a more intimate contact between the cathode mix and the electrolyte. This breaking up does not take place until after the paste has gelatinized or set, and consequently there is no danger that this rupture of the plaster coating will allov7 carbonaceous material or manganese depolarizcr to pass over into direct contact with the zinc.

A mixture that I have found to give satisfactory results consists of 500 grams plaster and 700 cubic centimeters of a 2% starch solution. Or, I may use a magma consist-v ing of 250 grams starch, 225 grams plaster and 650 cubic centimeters of 2% borax solution. As another example, I -may use 20 grams plaster and 50 grams of starch suspended in 100 cubic centimeters of a 10% deXtrin solution.

Other colloids will act similarly with other electrolytes, but the use of starch to be acted on by zinc chlorid in shattering the hardened dip is the embodiment preferred by me.

When agar agar is used as the colloidal suspension to prolong the time of setting, this shattering of the coating does not take place, for agar agar is inert with respect to the electrolyte. It does, however, produce a semi-permeable membrane which allows the transfer of ions, and with certain electrolytes and under certain conditions it may be desirable to have such a semi-permeable membrane rather than to have the coating 'broken up through expansion of some of its components. As illustrative of the use of agar agar, a mixture of the following composition may here be mentioned. 500 grams plaster, as plaster of Paris; 7 grams agar agar, and 7 00 grams water.

As a modification of the procedure above outlined, I have found that the cores can be dried in air when suspended by the carbon electrode, and, therefore, need not rest on a greased plate, or on a layer of sand.v This allows the coating to ow toward the bottom and harden into a nodule or enlargement as indicated diagrammatically at 11, Fig. 2. As a result, the coating is thicker onthe bottom orend of the cylinder than it is 011 the sides. This acts as a spacer and keeps the core farther from the bottom of the zinc can than it would be if the coating were the same thickness throughout. If desirable, the bottom can be paratffined, as explained in Burgess Patent No. 1,162,449, to prevent eX- cessive action, but satisfactory life of the battery is obtainable without doing this.

This method of making dry cells of the bag type eliminates the use of gauze, cheesecloth or like fabric, now expensive and difficult to obtain, and likewise eliminates all of the hand labor of wrapping the cores and binding them with thread, and because of the eXtreme thinness of the plaster film there is made available for useful purposes a considerable space which otherwise would be occupied by the inert cloth wrapping and its binder. With the gauze wrapping there is danger of the entrapment of air when the paste is poured in and any bubble of entrapped air not only cuts down the effectivearea of the electrode, but also is liable to set up local actions of an undesired character. With the smooth plaster film= there is no danger of air entrapment. The

thickness of the film, being dependent on the viscosity of .the magma into which the core is dipped, is under easy control, particularly when a retarder is used to delay setting of the dip. A good contact is assured between the electrolyte and the cathode, and this is particularly the case when starch is incorporated in the coating, and by swelling under the action of thc zinc chlorid shatters the coating after the electrolyte has set to a consistency to hold the mixin position whether the coating is or is not present.

In practising the process above described and hereinafter claimed, various materials may be used for the dip and for the retarder and a means for ultimately shattering the core, and I contemplate such cl'langes in the process and inthe materials used as reasonably come within the spirit and scope of the present invention as defined by the claims appended hereto.

.The process herein described is claimed in my divisional application Serial No. 273,020, tiled January 25, 1919.

I claim:

l. A dry-cell cathode having a bibulous envelop of hardened dip.

2. A dry-cell cathode having a bibulous envelop consisting essentially of a hardened plaster dip.

3. A dry-cell cathode having a hard bibulous envelop of retarded plaster dip.

4. A dry-cell cathode having an adhering envelop consisting essentially of plaster of Paris and a suitable retarder.

5. A dry-cell cathode having an adhering en velop consisting essentially of plaster with an adlnixture of boraX.

G. A dry-cell cathode having an adhering envelop consisting essentially of plaster with an admixture of suitable colloioi.`

7. A dry cell cathode` having an adhering envelop consisting essentially of plaster with a suitable admixture on which zinc chlorid will act to render the envelop more porous when the cathode is vused in a dry 8. A dry-cell cathode having an adhering envelop consisting essentially of plaster with an admixture of starch.

9. A dry-cell cathode having an adhering envelop consisting essentially of plaster with an admiXture of agar agar.

10. A hardened electrode envelop for a dry-cell cathode, of about the composition 250 grams starch and 225 grams plaster of Paris and 650 cubic centimeters of two per cent. boraX solution, substantially as described.

11. A dip for a dry-cell electrode having a composition approximating 250 grams starch, grams plaster of Paris and 650 cubic centimeters of two per cent. boraX solution, substantially as described.

12. A dry-cell having a zinc electrode, a cathode core therein, an electrolyte about said core, and grains of sand separating said core from said electrode.

l 13. A dry-cell having a zinc electrode, a cathode therein having a bibulous envelop consisting essentially of hardened plasterv dip, a suitable electrolyte, and grains of sand adhering to seid dip and spacing said cathode from said electrode.

14. A dry-cell having zinc electrode, a molded cathode therein, a bibulous envelop adhering to said cathode and consisting essentally of plaster of Paris and a suitable retarder, and a gelatinized electrolyte between sad zinc electrode and said cathode.

15. A dry-cell having a zine electrode, a

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molded cathode therein, a bibulous envelop adhering to said cathode and consisting essentially of plaster, starch and boraX, and a gelatmized electrolyte for said cell oontaining zine ehlord, substantially as described.

In testimony whereof ll ax my signature.

ARLIE WLLAM SGHORGER. 

